OBJECTIVES: 1) Thirty-five previously unstudied compounds were investigated for dopamine receptor activity. 3-4-Dihydroxynomifensine was found to be an active agonist of dopamine vascular receptors. Other active compounds were N-substituted derivatives of dopamine and A-6,7-DTN, and 1-aminomethylisochromans. Substitution of fluorine on the 2 position of the benzene ring of norepinephrine yielded a derivative active on beta1- and beta2-adrenergic receptors; fluorine on the 6 position yielded an agent active only on alpha-adrenergic receptors. 2) The source of catecholamine innervation of the kidney was traced and found to derive either from abdominal splanchnic nerves or from a small ganglia associated with the adrenal gland. 3) Investigation of a stable analog of PGI2, 10,10-difluoro-13,14-dehydro PGI2, indicated that it had a much longer duration of action in vitro than PGI2, but did not have a more prolonged effect than PGI2 in the intact dog. 4) Studies of breath tests in newborn rats and mice in which mothers were treated with a variety of xenobiotics demonstrated pronounced effects on newborn metabolism of caffeine and aminopyrine. Administration of alcohol to the mother produced pronounced effects on aminopyrine metabolism in the newborn. 5) Clinical studies of non-invasive breath tests in humans indicated that the aminopyrine breath test has clinical potential in diagnoses and prognoses of hepatic diseases.